1. Field of the Invention
The present invention relates to an optical sensor apparatus, and specifically relates to an optical sensor apparatus capable of obtaining high-quality images.
2. Description of the Related Art
The optical sensor apparatus has been used for solid-state image sensing devices which have a sensitivity for visible light. Recently, Life science-related field is increasingly attracting attention. Life science-related objects, such as drugs, foods, and living bodies, absorb light of an infrared wavelength range of approximately 1 μm to 3 μm. As the technology in the life science field is developed, the use of an infrared optical sensor apparatus has become widespread. The infrared optical sensor apparatus is usually cooled to, for example, liquid-nitrogen temperature during operation. With improvements in semiconductor technology, the infrared optical sensor apparatus has sufficiently high image quality, even if the infrared optical sensor apparatus is cooled by using thermoelectric device such as a Peltier device. In addition, the infrared optical sensor apparatus has become smaller in size. For example, “Two-Dimensional Near Infrared Sensor with Low Noise and Wide Wavelength Range”, SEI TECHNICAL REVIEW, NUMBER 76, pp. 98-101, APRIL (2013) by Yasuhiro IGUCHI et al. discloses an infrared image sensor that combines an infrared light receiving device (sensor chip) having a two-dimensional array of pixels with a complementary metal oxide semiconductor (CMOS device) device forming a read-out circuit (read-out integrated circuit (ROIC)). In this infrared image sensor, the sensor chip is flip-chip connected through indium bumps to the CMOS device. This sensor chip is mounted on a ceramic package together with a Peltier device. A photocurrent generated in each pixel of the sensor chip is output as a voltage through a capacitive trans-impedance amplifier (CTIA) in the read-out circuit, processed by an external field-programmable gate array (FPGA), and then output as a digital signal.
Optical sensor apparatuses, including those for the visible range, have been developed for better image quality. For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 6-302845) proposes an anti-reflection coating that absorbs reflected light to suppress noise light produced in the light receiving regions (pixels) of a solid-state image sensing device for visible light. Specifically, the proposed anti-reflection coating has a textured surface. Also, Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2003-163938) proposes a structure that provides a partition for each pixel unit to suppress crosstalk caused by scattered light.
Furthermore, Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2013-41922) describes a problem related to image quality of an infrared image sensor. In this problem, alight receiving device malfunctions due to infrared light entering through through-holes formed in a wiring board. As a solution to this, a light receiving apparatus is proposed, in which the through-holes are filled with resin that transmits visible light and blocks infrared light.